I personally feel *no one* should be allowed to drive, other than a computer. Unfortunately that is not possible at the moment, but it may be in a year or 5.
I spent most of the time behind the wheel looking at my fellow drivers. I trust them about as far as I can throw'em: not far. I've been rear-ended on the freeway, slammed into while waiting for trafiic lights, and had a frontal collision with an idiot who was overtaking. All were in their thirties.
As far as I can tell, about 5% are assholes, about 20% is too fearfull of driving, and about 20% is not paying attention while driving, the rest has to look out for all aforementioned idiots.
Age is but a small influence, compared to all other errors that can be made.